466 AMERICAN JOURNAL OF BOTANY

LITERATURE CITED

l \'01. s i.

AU'l'EXRIE"l'II, W., ANU W. H. WARREN. 19:28. Laboratorymanual for the detection of poisons and powerfuldrugs. (i00 pp. Blakiston, Philadelphia.

CROMWELL, B. T. 1943. Studies on the synthesis ofhyoscyamine in A tropa belladonna L. and DaturaHtramonium L. Biochem. Jour. 37: 717-7:29.

DAWSON, H. F. 1941. The localization of the nicotinesynthetic mechanism in the tobacco plant. Science94 : 396-397.

1949. Accumulation of nicotine in reciprocalgrafts of tomato and tobacco. Amer. Jour. Bot.:29: 66-71.

1944. Accumulation of anabasine in reciprccalgrafts of Nlcotian« .'flmwIl and tomato. Arne r ..Jour.Bot. (in press).

GurGN ARU, L. 1907. Recherches physiologiques sur lagreffe des plantes it acide cyanhydrique. Ann. Sci.N at. Bot., Paris (9" serle) 6: 961-305.

HI EKE, K. 194:2. Pflanzenphysiologische Untersuchungentiber die Alkalotde. II. Zur Alkaloidfiihrung del'Pfropfpartner bei heteroplastischen Solanaceenpfro­pfungen. Planta 33: 185-:20.5.

KRAJEVOJ, S.•J., AND I. NECHAEV. 1941. Atropine trans­ference from stock (Daturu Stramonium) to scion(Solanum lycopenicum). Compt. Rend, (Doklady)Acad, Sci. URSS. 31: 69-71.

LINUE:>IU"l'H, H. 1906. tber angebliches Vorhandenseinvon Atropin in KartoffelknoIIen infolge von Trans­plantation und tiber die Grenzen del' Vcrwachsunjrnach dem Verwandschaftsgrade. Bel'. Deutsch, Bot.Ges, 24: 4:28-4315.

"fEYER, A., UND E. SCH:>IIIY1". 1907. Die Wanderung del'Alkalolde aus dem Pfropfreise in del' Unterhun-,Bel'. Deutsch. Bot. Ges. :21>: 131-137.

---, UNU ---. 1910. t"ber die gegenseitige Beciu­flussung del' Symbionten hetcroplastischer Trans­pJantationen mit besonderer Beriieksichtigung derWauderung der Alkaloide durch die Pfropfstellen.Flora (Jenu ) 100: 317-397.

SCHMUCK, A., D. KOWl"OF.', AND A. BOROZDIXA. 19~~9.

Alteration in the alkaloid compositlon due to theinfluence of stock upon scion in Nicot.iun«. Compt.Rend. (Doklady) Acad. Sci. URSS. :215: 477-·t80.

---, A. Sl)IIRNOV, ANi} G. ILYIN. 1941. Formation ofnlcotlne in plants grafted on tobacco. Compt. Rt·IH!.(Doklady ) Acad. Sci. URSS. 39: 36.5-368.

S'rRASBURGER, E. 18815. Ueber Verwachsungen und dcrenFolgen. Bel'. Deutsch, Bot. Ges, 3: 34-40.

1906. Zu del' Atropinnachweis in den Kartof­feIknoIIen. Bel'. Deutsch. Bot. Ges. :24: 1599-600.

A HETEROSPOROUS SPECIES OF BOWMANITES FROM THE MICHIGA~

COAL BASIN 1

Chester A. Arnold

THE VARIOUS members of the Sphenopsida, bothliving and fossil, are generally regarded as essen­tially homosporous, although it cannot be said thatheterospory is nonexistent within the group. InEquisetu m the spores produced by a single plantare alike in size, but they grow into gametophytessome of which bear only antheridia and others onlyarchegonia. The gametophytes are therefore dioe­cious even though true heterospory is not revealed.In the fossil genus Calamites a slight difference inspore size of some species has long been lookedupon as an indication of incipient heterospory, eventhough the two kinds of spores may occur withinidentical sporangia on the same sporangiophore.Other species of Calamites are believed to be strict­ly homosporous. In Sphenophyllum homospory isbelieved by most authors to have prevailed al­though heterospory has been reported in a few in­stances. Renault (1876) described and figuredwhat he thought was a megaspore within the spo­rangium of a fructification assigned to Sphenophyl­lum Dawsoni, but the object was evidently a mis­placed fragment of the sporangial wall. Severalyears later Thoday (1906) observed a differencein spore size within a sporangium attributed to thesame species. In one sporangium the spores rangedup to 120 micra in diameter but averaged 106 mi­cra, and in the adjacent sporangium the average

1 Received for publication April 99, 1944.

size was 83 micra. Zobel (1910) figured what hesupposed were the microsporangia and megasporan­gia of S. verticillatum, but as he found spores onlywithin the former, heterospory, though suggested,was not demonstrated. Lacking indisputableevi­dence, therefore, of heterospory in Sphenoph.ylllllll,most authors have concluded that homospory musthave been the rule throughout this group of plants(Scott, 1920; Walton, 1940; Hoskins and Cross,191.3). Hoskins and Cross include homospory as ageneric character in their revised diagnosis of theorgan genus Bowmanites to which they refer allfructifications attributable to Sphenophyllllm. Afew authors, on the other hand, make some allow­ances. Hlrmer (1927) cites S. oeriicillatum as anisolated example of heterospory within the genus,and Eames (1936) says that although most spe­cies are homosporous, a few are known to have heenheterosporous. Although Eames cites no examples.his generalization is now known to be correct.

The present account is concerned with a spheno­phyllaceous fructification which is distinctly hetero­sporous. Not only is the phenomenon clearly demon­strable, but it is as pronounced, as far as differencein spore size is concerned, as in the recent lycopodSelaginella. This instance merely shows that in theSphenopsida, and within Sphenophyllum in par­ticular, both homospory and well-defined hetero­spory existed. Differences in spore size may not

Od.,19-14] ARNOLD-BOWMANITES 467

necessarily be correlated with any observable dif­ferences in the size of the sporangia, and there isno evidence whatsoever in our material of segrega­tion in different parts of the strobili.

Souncn.-c-The fructifications described in thisaccount came from a shale bed below the "lowerLingula layer" in the quarry of the Grand LedgeClay Products Company, at Grand Ledge, Michi­gan. This shale lies just below Cycle "A" of thePre-Verne cyclical formations of the Saginaw groupas outlined by Kelly (1936) and is of Pottsville(early Pennsylvanian) age. This horizon hasyielded a flora of considerable size.

DESCRIPTION.-The material consists of frag­ments of a number of individual strobili preservedas carbonized compressions (fig. 1, 2). None of thestrobili are complete, and none are attached to thevegetative parts. This detached and fragmentarycondition suggests that the organs were transportedfor some distance before they sank into the muddybottom. In a few specimens believed to belong tothis species the whorls of coalescent sterile bractsare partially preserved, but preservation is inade­quate to reveal the exact relation of the sterilebracts and the sporangiophores. On most of thespecimens, only the sporangia are preserved, andinferences concerning the morphology and affini­ties are drawn mostly from the gross aspect and thearrangement of the sporangia.

The strobili are approximately 1.70 em, broadand at least 10 em. long, although none were foundcomplete. It is unlikely, however, that any of themwere originally much longer. The sides are parallelfor most of the length and the bases and apices arerather abruptly rounded. The sporangia are ar­ranged in verticels spaced at intervals of about 5mm. The sporangiophores are not preserved, but itis evident from the packed condition and the largenumber of sporangia per whorl that the stalks wereof different lengths, with shorter ones bearing spo­rangia near the axis and longer ones bearing othersat the outer circumference of the verticel. Thereare many sporangia per verticel; although the num­ber can only be crudely estimated, there are at leastsixty and maybe more. In those specimens withwell preserved sporangia nothing remains of theintervening whorls of bracts which subtended thesporangiophores.

The sporangia are ovoid bodies measuring 1.75by 2.50 mm., and appear to be borne in pairs on theupturned distal ends of the sporangiophores. Inmany of the specimens the individual sporangia canbe lifted as tissue-thin bodies with the point of aknife blade or a dissecting needle. Several of thesewere placed singly in test tubes and treated withSchulze's reagent (potassium chlorate and concen­trated nitric acid). The maceration process re­moved the dark coloring matter and revealed thespore contents, and in this way it was possible todetermine the kind of spores present in each one.Due to the fact that the carbonized material of the

fructifications consists almost wholly of the com­pressed sporangia, and since these could be re­moved from their original position free from ex­traneous matter, there is no alternative but that thetwo kinds of spores observed belong to the samefructification. The verticillate arrangement and thepacked condition of the sporangia are shown infigures 1 and 2. This specimen is incomplete andlacks both the apex and base, but it is selected asthe type because of the clarity with which the spo­rangia are shown.

The sphenophyllaceous affinities of the fructifica­tion are obvious from the size, number, and arrange­ment of the sporangia within the verticels. In fact,in no sphenopsid fructifications except those as­signed to Sphenophyllum are the sporangia everarranged in concentric circles within the verticels,This arrangement is due to the fact that each sterilebract bears more than one axillary sporangiophore(although some species possess but one) and theyare of unequal length, well known examples beingBowmanites Dawsoni, B. Riimeri and B. trisporan­giatus, the latter recently described by Hoskins andCross (1943). There is no evidence whatsoever inour material of the peltate type of sporangiophorefound in Calamites and Equisetum.

Upon prolonged maceration the sporangial walldissolves away and the masses of cutinized sporescontained within are freed. Most of the sporangiacontain a large number of very small round smooth­walled spores which range from 75 to 90 micra indiameter (fig. 3, 5). Figure 3 shows the contentsof a single microsporangium enlarged twenty-fivetimes. The spores are very loosely held together,and unless carefully handled the mass disinte­grates. Many of them still adhere in tetrads (fig.9). It should be noted that these microspores agreeclosely with the dimensions usually given for thoseSphenophyllum spores which are usually regardedas isospores. Hoskins and Cross (1943), who havebrought together practically all of the publisheddata on spore size in the fructifications of Spheno­phyllum give the following dimensions:

Bowmanites Scottiir----65-85 micra including perisporeB. Dawsoni-75-100 micra including perisporeB. trisporangiatus-l00-150 micra including perispore

75-195 micra without perisporeB. Riimeri--l00 micraB. fertilis-90-96 X 65-70 micra without perispore

The perispore is not included in the dimensionsgiven for our material and the existence of thislayer is problematic, but it seems significant to notethat the dimensions (75-90 micra) are about theaverage for those given for the genus as a whole.

A few of the sporangia, probably one amongevery eight or ten present in the carbonized stro­bili, contain large spherical or slightly ovoid sporeswhich range in size from 580 X 665 micra to 750X 750 micra. Figure 6 shows the contents of such asporangium enlarged twenty-five times (the sameas fig. 3 which shows the microspores ). These large

168 AM E R IC AN JO URNAL OF BOTANY [Vol. 31.

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Fig. l -!l.-Fi~. 1. Enlarged view of holotype specimen showing th e closely packed, verticillateIy a r ranged, ovalsporanala . X g.9.- F ig . 2. Sp ecimen shown in figure 1. Natural size.- -F ig . 3. Contents of a single mi crosporangiumfreed hy maceration. X g5.-Fig . .l, Si ng le megaspore sho wing tetrad sca r. X 6-l.-Fig. 5. I solated microspores. X6-l.-Fig-. 6. Contents of a single mcgnsp oranglum showing th e fully formed and aborted megasp ores. X g5.-F ig. 7.Sin gle mejra spo re. X 64.-Fig. 8. Aborted megaspore. X 64.-Fig. 9. Mlcr ospore tetrad. X g40.

sp ores, the megaspores ( fig . '!-, 7 ) , have thin smoothwalls, and show a con spicuous tetrad sca r . Abouts ixtee n of these megaspores appear to be presentwi th in II sporangium althoug h th e exa ct number is

uncertain. Not all of the megaspores reached ma­turity. W ithin the mas s, among the fully formedspores , there are a few aborted members which are 'about one -t hird as large as th e fully formed ones

Oct., j9~~ I ARNOLD-BOWMANITES 4,69

(fig. 8). At least two aborted megaspores may beseen in figure 6. One lies at the bottom of the figureslightly detached from the mass, and another ap­pears as a triangular opaque area near the upperright side. Not all of these aborted spores are tri­ungular, Many are rounded like the mature ones,but their walls are always slightly darker and lessreadily bleached during the maceration process.Each megaspore is probably surrounded by a peri­spore, but little or nothing has been determinedconcerning the character of this layer. Its presenceis suggested in some instances by fragments of dis­organized material around the exine.

It is evident that as far as spore size is con­cerned, heterospory is as well developed in thisform as in many of the ancient and modern lyco­pods (Lepidodendron, Selaginella, etc.). There is,however, no discernible difference in the externalappearance of the sporangia bearing the two types,nor is there any apparent segregation in differentparts of the cones. The megaspores and microsporesare borne in sporangia alike in size and shape, andin the same verticels.

Although the structure of large organs cannot beworked out with the same degree of exactitude bymaceration of carbonized remains as with thin sec­tions of petrifactions, the maceration method is notwithout distinct advantages. It enables one to exam­ine a much wider range of materials than is usuallypossible with sections, and in addition such objectsas spores can be observed in their entirety and largequantities measured. This is rather difficult in thinsections. Maceration, of course, requires care on thepart of the investigator to eliminate extraneousmaterial, but in a situation such as that under con­sideration here, the different parts can be handledindividually, so there is no cause to question thevalidity of the results obtained. If only a few largespores were to be observed among a multitude ofsmaller ones, their presence could be explained asaccidental, but when they occur in abundance andcan be observed in situ within the original sporan­gia which were individually removed from the fruc­tification, they may be accepted as proof of a trueheterosporous condition.

TAXONOMY.-The fructification described here isreferred to the organ genus Boiomaniies (Binney,1870). This name, according to Hoskins and Cross(1943) is the correct one for detached sphenophyl­laceous strobili, as it has priority over Sphenophyl­lostachys which was proposed by Seward (1898).rolkmannia, a name of still older standing, wasfounded upon organs now known to belong to Cala­mites. However, in assigning this material to Bow­manites, it is necessary to broaden the concept ofthe genus as given by Hoskins and Cross so as toadmit heterosporous forms. The only other alterna­tive is to create for our material a new genus whichis considered inadvisable for at least two reasons.I n the first place, our form is not sufficiently pre­served to serve as a generic type, and secondly,

homospory is not such a constant feature amongthe sphenophylls as Hoskins and Cross have as­sumed. It has already been pointed out that themicrospores in our form are similar in size to thealleged isospores of some of the other species. Atpresent it is impossible to divide Bowmanites onthe basis of spore condition, because in no otherspecies have spores been reported that in any wayapproach the megaspores of our form in size. It isquite probable that such types as BotomanitesScottii and B. fertilis might be found to be hetero­sporous were the spore condition in these fullyknown, and the same might be predicted for B.Romeri which apparently is known from a verylimited amount of material. The generic diagnosisof Boiomaniies should be broad enough to includeboth homosporous and heterosporous forms.

BOWMANITES delectus sp. nov.-Strobili large,about 1.70 em, in diameter and at least 10 em, long,linear; sporangia ovoid, 1.75 X 2.50 mm., bornein pairs and in whorls spaced at intervals of 5 mm.on the axis, numerous (60 or more per whorl) andclosely packed; heterosporous; megasporangia andmicrosporangia similar except for spore contentand produced in the same whorls; microspores nu­merous, 75-90 micra in diameter, smooth; mega­spores spherical or slightly ovoid, thin walled,smooth, 660-750 micra in greatest diameter, about16 in each sporangium; a few aborted megasporeshaving about one-third the diameter of the matureones; perispore probably present; tetrad scar con­spicuous in both types. Holotype No. 23115 Univer­sity of Michigan Collection.

DEPARTMENT OF' BOTANY AND MUSEUM m' PALEONTOLOGY,UNIVERSITY OF MICHIGAN,

ANN ARBOR, MICHIGAN

LITERATURE CITEDBINNEY, E. W. 1870. Observations on the structure of

fossil plants in the Carboniferous strata. Part II.Lepidoetrobus and some allied cones. Paleont. Soc.24: 33-60. London.

EAJ>IES, A. J. 1936. Morphology of vascular plants.Lower groups. New York and London.

HIRMER, M. 1927. Handbuch del' Paluobotanlk, Miinchenund Berlin.

HOSKINS, J. H., AND A. '1'. CROSS. 1943. Monograph ofthe paleozoic cone genus Bsnomanites (Sphenophyl­lales). Arner, MidI. Nat. 30: 113-163.

KELLY, W. A. 1936. Pennsylvanian system in Michigan.Ann. Rept. Michigan Geol. Surv. Div., Dept. Conser.Publ. 40, Ser, 34: 155-2:26. Lansing.

RENAuL'r, M. B. 1876. Nouvelles recherches sur lastructure des Sphenophyllum et sur leur affinitiesbotanique. Ann. Soc. Nat., Bot. Ser, 6, 4: 277-311.

Scur-r, D. H. 1920. Studies in fossil botany. Vol. I,3rd Ed. London.

SEWARD, A. C. 1898. Fossil plants. Vol. I. Cambridge.'fUODAY, D. 1906. On a suggestion of heterospory in

Sphenophyllum Doseeoni. New Phytol. 5: 91-93.WALTON, J. 1940. An introduction to the study of fossil

plants. London.ZOBEL. A. 1910. Sphenophyllum verticillatum. Abhandl.

und Beschreib. Foss. Pflanzen (by R. Potonie). Lief.VII, Nr. 138. Berlin.

470 AMERICAN JOlTRNAL OF BOTANY [\'01. ai,